Experimental study on nonlinear−optical property of Ag4P2Se6

Mid−infrared (MIR) nonlinear optical (NLO) material is critical to laser frequency−conversion technology. Although the main commercial MIR NLO crystals (AgGaS₂ AgGaSe₂ and ZnGeP₂) are practically used, they still have some intrinsic drawbacks, so that it is of great scientific significance to discover new materials with good MIR NLO performances. Among the main systems of chalcogenides to explore MIR NLO crystals, metal thiophosphates and selenophosphates are competitive for their structural diversities and strong covalent P−Q bonds. Here, Ag₄P₂Se₆ (P2₁2₁2₁) was selected to evaluate the second−order harmonic generation (SHG) property. As a result, the SHG response with phase−matching ability is about 0.5 times that of AgGaS₂ at 2.05 μm in the particle range of 210–270 μm, and the laser damage threshold (LDT) is larger than that of AgGaS₂. Remarkably, this compound is of low melt temperature of 642 °C with a congruent melting character, also possesses excellent chemical stability, facilitating its further crystal growth and fabrication.